For 'most' seeds it is 24/25 or so seeds, but there are many exceptions. Many folks are satisfied to receive a smaller quantity as it really just depends upon the person, the seed, the cost of the seed if it is commercially bought, one's desire, etc.

Per the FAQ here:
How many seeds are considered a 'fair' trade?

A fair trade is whatever you and the other trader agree to. Generally, two to three dozen seeds should be enough to ensure germination and growth of a satisfying number of plants. However, the most certain way to assure both parties will be satisfied is to discuss quantities when negotiating the trade.

Communication is most important so both traders are happy with the trade.

I have several things that I trade in quantities of less than 25 seeds. It is noted on my Trade List, what the quantities are if they are less than 25 or so.

Here is a fairly recent thread discussing seed quantities and different 'special' seeds.

Thank you Sue,
that is very helpful!
It covers lots of different situations - so there is no one answer to my Q, I understand.
Some seeds are very tiny, and I was wondering: how in a world do I count those. Or do I need to weigh them? Or calculate based on "tea spoon" amount?
I do want to be generous with my trades and offers, I just did not have a conception of what that is in terms of amount of seeds.
So, thank you Sue! A bucket-full of seeds thank you :-)!

Some seeds are very tiny, and I was wondering: how in a world do I count those.
Yes, like sedum that are the size of dust, or butterfly bush seeds, that look like short pieces of very thin hair. Even sending 25-50 or more of those doesn't look like anything at all.

I have had members trade/share maybe 15 or so poppy seeds with me and I was thrilled. They were special hybrid varieties and had been purchased commercially. The amount one gets when buying commercially might be quite small, so I was thrilled with what I got.
Often when members save seeds from poppies they have an abundance of seeds. In a case such as members trading saved poppy seeds, quantities vary greatly. Some might send 1/8ts, others 1/4ts, and others might send a whole bunch! I received a massive amount in a trade last fall, and there were so many that I saved myself a few, and have the rest listed for trade and I send 1/4ts.

Often a member only really wants or needs enough to get a few plants going, so they can then save seeds themselves.

Yes...good communication assures no one being disappointed in seed quantity.

the bigger the seeds are the less the amount also. if your sending one the size of a quarter, your definately not sending 25 of those!! **smile**
and say, if they are the size of a dime. same thing.
a lady and i have a trade that is gong on, and she sent me 3 of the tomato seeds that i asked for. it definately wasn't what i expected, but let me tell you, i was more than happy!! because they were some of the MOST wanted!! and she sent me an uneven trade, hers being more. and mine being less. so let me tell ya, i'm like wayyyyy happy!! LOL i like to ask and make sure.
just make sure that you don't get caught up in all the fun and get all addicted!! and watch out for some people!! i won't mention any names. they are nuts and they like to send ya all these extra seeds!! **onery grinn** they are known as "enablers" **big smile** ~Medo

I am personally thrilled to receive as much and whatever people can/willing to send me. I am very grateful for anything - feel like a kid on Christmas morning!
My main concern was unknowingly sending less then is considered a norm to someone, and somehow unintentionally offending them and creating an image of a "cheap skate" :).
Knowing so little about the proper etiquette of seed trading, it is easy to miss the mark and... well, you know.
So, thank you all for enlightening me!
~Natalie